This chapter focuses on the pathogenesis, diagnosis, and management of central nervous system (CNS) toxoplasmosis. The latest epidemiological trends are discussed, and special attention is given to recently developed diagnostic modalities including laboratory techniques and newer neuroimaging modalities. The lesions associated with toxoplasmosis vary in size, characteristics, and location. Typical lesions of toxoplasmosis are characterized histopathologically by three zones. In patients with AIDS, toxoplasmosis is almost always due to reactivation of previously acquired infection. Manifestations of toxoplasmosis in the AIDS population are primarily those of CNS dysfunction and usually reflect the multiple abscesses that are present. Given the high seroprevalence of toxoplasmosis, positive serology is not helpful in distinguishing reactivation from quiescent infection and is not very useful in ruling in active Toxoplasma infection. The locations of lesions adjacent to cerebrospinal fluid (CSF) pathways, e.g., periventricular as well as subependymal spread or ventricular encasement, are characteristic of primary CNS lymphoma (PCNSL), rather than toxoplasmosis. Thallium-201 single photon emission computed tomography (Tl-SPECT), fluorodeoxyglucose positron emission tomography (FDG-PET), and magnetic resonance spectroscopy have all been studied as methods to differentiate PCNSL from other causes of focal brain lesions, specifically toxoplasmosis. For patients who have not received HAART, primary prophylaxis and maintenance therapy need to be continued indefinitely due to the high risk of acute toxoplasmic encephalitis (TE) and relapse of TE, respectively.

Postmortem brain showing a lesion of untreated toxoplasmosis involving the basal ganglia. There is significant surrounding edema and mass effect with compression of the ipsilateral ventricle. (Reprinted with permission from Rushing and Burns, 2001.)

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FIGURE 2

Postmortem brain showing a lesion of untreated toxoplasmosis involving the basal ganglia. There is significant surrounding edema and mass effect with compression of the ipsilateral ventricle. (Reprinted with permission from Rushing and Burns, 2001.)

References

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107. Olatinwo,T.,, M.Herbowy, and, R.Hewitt.2001.Toxoplasmic encephalitis and primary lymphoma of the brain—the shift in epidemiology: a case series and review of the literature.AIDS Read.2001:444– 449.